Effects of chronic administration of β-blockers on airway responsiveness in a murine model of heart failure

An overview of the efficacy and safety of β2-adrenoceptor antagonists for the treatment of chronic obstructive pulmonary disease

INTRODUCTION

The safety of β2-AR antagonists in the treatment of patients with COPD continues to be a topic of research and discussion within the medical community. Emerging evidence suggests potentially benefits in the management of this complex respiratory condition. However, antagonists that display a preference for β2-AR over β1-AR present a complex therapeutic challenge in COPD management, necessitating an understanding of differences in their pharmacological profiles and clinical implications.

AREAS COVERED

An overview of the mechanisms of action of β2-AR antagonists and their potential impact on respiratory function, their pharmacological interactions, clinical implications, and future perspectives in COPD.

EXPERT OPINION

β-Blockers have the potential to become a versatile class of therapeutic agents with benefits beyond their original cardiovascular use. However, the one-size-fits-all approach of prescribing β-blockers regardless of their receptor selectivity to COPD patients with concomitant heart disease may not be appropriate. Instead, it is advisable to develop an individualized treatment strategy based on a thorough assessment of the patient's overall health. The use of non selective β2-AR antagonists, functioning as inverse agonists at β2-ARs, has garnered interest and debate, but further research efforts should focus on elucidating the optimal use of β-AR antagonists in COPD, balancing cardiovascular benefits with potential respiratory risks to enhance outcomes and quality of life for individuals living with this debilitating respiratory condition.

Carvedilol and metoprolol are both able to preserve myocardial function in type 2 diabetes

PURPOSE

Increasing cohorts of patients present with diabetic cardiomyopathy, and with no targeted options, treatment often rely on generic pharmaceuticals such as β-blockers. β-blocker efficacy is heterogenous, with second generation β-blocker metoprolol selectively inhibiting β₁ -AR, while third generation β-blocker carvedilol has α₁ -AR inhibition, antioxidant, and anti-apoptotic actions alongside nonselective β-AR inhibition. These additional properties have led to the hypothesis that carvedilol may improve cardiac contractility in the diabetic heart to a greater extent than metoprolol. The present study aimed to compare the efficacy of metoprolol and carvedilol on myocardial function in animal models and cardiac tissue from patients with type 2 diabetes and preserved ejection fraction.

METHODS

Echocardiographic examination of cardiac function and assessment of myocardial function in isolated trabeculae was carried out in patients with and without diabetes undergoing coronary artery bypass grafting (CABG) who were prescribed metoprolol or carvedilol. Equivalent measures were undertaken in Zucker Diabetic Fatty (ZDF) rats following 4 weeks treatment with metoprolol or carvedilol.

RESULTS

Patients receiving carvedilol compared to metoprolol had no difference in cardiac function, and no difference was apparent in myocardial function between β-blockers. Both β-blockers similarly improved myocardial function in diabetic ZDF rats treated for 4 weeks, without significantly affecting in vivo cardiac function.

CONCLUSIONS

Metoprolol and carvedilol were found to have no effect on cardiac function in type 2 diabetes with preserved ejection fraction, and were similarly effective in preventing myocardial dysfunction in ZDF rats.

Expression of β1- and β2-adrenergic receptors in the lungs and changes in the levels of corresponding autoantibodies in an aged rat model of heart failure

β-adrenergic receptors (β-ARs) and anti-β1-AR autoantibodies play important roles in heart failure. This study was designed to investigate the expression of β1- and β2-ARs in the lungs, and their relevance to the corresponding autoantibodies in an aged rat model of heart failure. In addition, we investigated the association between anti-β-AR autoantibody and soluble Fas (sFas) and soluble Fas ligand (sFasL). Aged male Wistar rats were divided into the sham-operated control group and the heart failure group. At 0 and 9 weeks post-surgery, the protein levels of β1- and β2-ARs in the heart and lungs were measured by western blot analysis. The plasma concentrations of autoantibodies, sFas and sFasL were determined by enzyme-linked immunosorbent assay (ELISA). The protein levels of pulmonary β1- and β2-ARs were decreased in the heart failure group when compared with the control group (P<0.01). Both the frequencies of the occurrence and the titers of autoantibodies against β2-AR increased at 9 weeks post-surgery (P<0.01). The levels of sFas and sFasL were also elevated, although there was no difference in the levels of sFas and sFasL between the groups, with positive and negative anti-β-AR autoantibody. These findings suggested that during the development of heart failure, the densities of pulmonary β1- and β2-ARs decreased. The levels of anti-β2-AR autoantibody exhibited similar changes as those of anti-β1-AR autoantibody, and there was no definite association between anti-β-AR autoantibody and the levels of sFas/sFasL.

β2-adrenoceptor in obstructive airway diseases: Agonism, antagonism or both?

Obstructive airway disease is a complex disease entity including several maladies characterized by bronchoconstriction and abnormal airway inflammation. Reversing bronchoconstriction leads to symptomatic relief and improvement in quality of life, both in reversible (bronchial asthma) and partially reversible (chronic obstructive airway disease) obstructive airway diseases. β₂-adrenoceptor expressed in human airway is the main β-receptor subtype, and its activation in airway smooth muscle cells leads to bronchodilatation. Drugs targeting β-adrenoceptors have been around for many years, for which agonists of the receptors are used in bronchodilation while antagonists are used in cardiovascular diseases. This review article summarizes the effect and usage of β₂-agonist in obstructive airway disease, addressing the benefits and potential risks of β₂-agonist. The article also looks at the safety of β-blocker usage for cardiovascular disease in patients with obstructive airway disease. There is also emerging evidence that non-selective β-blockers with inverse agonism ironically can have long-term beneficial effects in obstructive airway disease that is beyond cardiovascular protection. Further trials are urgently needed in this area as it might lead to a dramatic turnaround in clinical practice for obstructive airway diseases as has already been seen in the usage of β-blockers for heart failure.

Effect of Prolonged Moderate Exercise on the Changes of Nonneuronal Cells in Early Myocardial Infarction

Myocardial infarction (MI) is one of the leading causes of death in developed countries and it is characterized by several associated symptomatologies and poor quality of life. Recent data showed a possible interaction between infarction and brain inflammation and activity. Previous studies have demonstrated the beneficial effect of exercise training on deterioration in cardiac function after MI. In this study we analyzed in sedentary and trained rats the microglia and astrocytes 48 hours after MI in PVN, thalamus, prefrontal cortex, and hippocampus through immunofluorescence approach. We found significant changes in specific microglia phenotypes in the brain areas analyzed together with astrocytes activation. Prolonged exercise normalized these morphological changes of microglia and astrocytes in the prefrontal cortex, hippocampus, and thalamus but not in the PVN. Our data suggest that there is an early brain reaction to myocardial infarction induction, involving nonneuronal cells, that is attenuated by the prolonged exercise.

Effects of chronic treatment with the new ultra-long-acting β2 -adrenoceptor agonist indacaterol alone or in combination with the β1 -adrenoceptor blocker metoprolol on cardiac remodelling

BACKGROUND AND PURPOSE

The ability of a chronic treatment with indacaterol, a new ultra-long-acting β2 -adrenoceptor agonist, to reverse cardiac remodelling and its effects in combination with metoprolol, a selective β1 -adrenoceptor antagonist, were investigated on myocardial infarction in a rat model of heart failure (HF).

EXPERIMENTAL APPROACH

We investigated the effects of indacaterol and metoprolol, administered alone or in combination, on myocardial histology, β-adrenoceptor-mediated pathways, markers of remodelling and haemodynamic parameters in a rat model of HF. Five groups of rats were assessed: sham-operated rats; HF rats; HF + indacaterol 0.3 mg·kg(-1) ·day(-1) ; HF + metoprolol 100 mg·kg(-1) ·day(-1) ; HF + metoprolol + indacaterol. All pharmacological treatments continued for 15 weeks.

KEY RESULTS

Treatment with either indacaterol or metoprolol significantly reduced the infarct size in HF rats. However, the combination of indacaterol and metoprolol reduced the infarct size even further, reduced both BP and heart rate, reversed the decrease in ejection fraction, normalized left ventricular systolic and diastolic internal diameters, normalized the decreased β1 adrenoceptor mRNA expression as well as cardiac cAMP levels and reduced cardiac GPCR kinase 2 expression, compared with the untreated HF group.

CONCLUSION AND IMPLICATIONS

The results of our study demonstrated an additive interaction between indacaterol and metoprolol in normalizing and reversing cardiac remodelling in our experimental model of HF. The translation of these findings to clinical practice might be of interest, as this combination of drugs could be safer and more effective in patients suffering from HF and COPD.